Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
To provide cellular wireless communication service, a wireless service provider or “wireless carrier” typically operates a radio access network (RAN) that defines one or more coverage areas in which wireless communication devices (WCDs) can be served by the RAN and can thereby obtain connectivity to broader networks such as the public switched telephone network (PSTN) and the Internet. A typical RAN may include one or more base stations (e.g., macro network cell towers and/or femtocells), each of which may radiate to define the coverage areas in which WCDs can operate. Further, each coverage area may operate on one or more radio carrier frequencies (e.g., radio frequency radiation patterns from a respective base station antenna). The base stations may then be coupled with a controller, which may then be coupled (e.g., directly or indirectly) with a switch or gateway that provides connectivity with a transport network such as the PSTN or the Internet. When a WCD, such as a cellular telephone, pager, or wirelessly-equipped computer, is positioned in a coverage area, the WCD communicates via a radio frequency air interface with the base station antennae of the coverage area. Consequently, a communication path can be established between the WCD and the transport network, via the air interface, the base station, the controller, and the switch or gateway.
In general, air interface communications in each coverage area of a cellular wireless communication system can be encoded or carried in a manner that distinguishes the communications in that coverage area from communications in adjacent coverage areas. For example, in a Code Division Multiple Access (CDMA) system, each coverage area has a respective pseudo-random noise offset or “PN offset” that is used to encode or modulate air interface communications in the coverage area distinctly from those in adjacent coverage areas. As another example, in a Long-Term Evolution (LTE) system, each coverage area is associated with a respective reference signal. Analogously, in other air interface protocols, communications in one coverage area may be distinguished from those in other coverage areas by frequency, time, and/or various other parameters. Further, a WCD may use one or more of the distinguishing parameters as a basis for detecting coverage of individual coverage areas (e.g., so as to facilitate evaluation of radio carrier frequency characteristics).
After registering in a particular coverage area, and while operating on a particular carrier frequency in the particular coverage area, the WCD may regularly scan for other coverage areas operating on the same carrier frequency. The WCD may continue to monitor the pilot signal or reference signals of the particular coverage area (e.g., the serving coverage area of the WCD) as well as the pilot signal or reference signals of adjacent coverage areas, and may at some point transmit to the serving base station or RAN a report indicating the strength of the monitored signals. For example, in a CDMA system, the WCD may transmit a pilot-strength-measurement message or data-rate-control message to the RAN. As another example, in an LTE system, the WCD may transmit a radio measurement report to the RAN. If the RAN determines, based on such reports, that an adjacent coverage area provides sufficiently stronger coverage than the currently serving coverage area of the WCD, the RAN may arrange for a handoff of the WCD to the adjacent coverage area.